1. Field of Invention
The present invention relates to the wireless power transmission and feedback technology, and more particularly to a wireless charging circuit adapted for a mobile power bank and a mobile power bank using the same.
2. Related Art
Wireless charging technology is a technology for charging device by electromagnetic field without any wire. Wireless charging technology is evolved from the wireless power transmission technology to use the magnetic resonant to transmit the electrical charge from charger to device to resonate coil and capacitor between the charge and device to achieve a high efficient power transmission. The wireless charger is more safer, no exposed connections, no leakage current. Thus, a lot of problems in wired charger is prevented.
Due to the development of the wireless charging technology, Wireless Power Consortium is established because of the situation. One of accomplishments of Wireless Power Consortium is to promote Qi standard. With the standardization, wireless charging technology is more widely adopted.
Additionally, since the mobile power bank is widely used, many manufacturers want to launch a product combining the wireless charging circuit and mobile power bank. The mobile power bank adopts the battery to be the main power source. Generally, the battery supplies 3.7V. However, the wireless charging circuit needs 5V input voltage to operate. Thus, between the wireless charging circuit and the battery, it must design a DC to DC converter. FIG. 1 illustrates a circuit diagram depicting a wireless charging circuit according to a conventional art. Referring to FIG. 1, in this circuit diagram, a boost DC to DC converter 103 is implemented between the battery 101 and the wireless charging circuit 102. When the wireless charging circuit 102 detects whether a wireless power receiver is disposed on the wireless charging circuit 102 or not, the boost DC to DC converter 103 must be enabled so that the detection can be performed. Thus, if an external object is disposed on the wireless charging circuit, the boost DC to DC converter 103 would be enabled. It causes the conversion loss and then the usage time of the power bank is decreased.